Our future and our evolutionary history

PARTICIPATING AUTHOR: JACK HAILMAN

Jack P. Hailman is Professor Emeritus of Zoology, University of Wisconsin, and Research Associate, Archbold Biological Station. He is the author of Coding and Redundancy: Man-made and Animal-Evolved Signals(May 2008)
Ever since popular literature and media began dealing with the subject of sex, there has been explicit recognition that the so-called hourglass
figure of women is an important, if somewhat idealized, sex attractant. Even before popularizations, of course, women knew this at leastimplicitly, which fact gave rise to devices of exaggeration such as bustles and "falsies." The higher tech equivalent of the latter, surgical implant, is still popular despite some health risks it entails. The interesting question is not what the signs are but why large buttocks and breasts are attractive to men. The long-known likely answer is that these traits once signaled important survival and
reproductive conditions. Fat reserves of the buttocks, for example, could see one through times of famine, and ample milk production is critical to survival of infants. Males were selected to mate with females who would most likely produce successful offspring, thereby perpetuating the male's genes. These feminine traits no longer predict the likelihood of reproductive success in a modern, developed country yet the ancestral masculine preference persists.

Natural selection shaped behavior of our evolving hominid species to its particular ecology, but if selection is still working at all today, it has not keep pace with demographic trajectories and technological advances. Explosive population growth overwhelms selective forces, and technology isolates us from many problems so that our behavior is not so closely adapted to the brave new worlds we have created. For example,
people still crave carbohydrates and fats as if they needed to identify scarce energy-rich foods in a harsh environment. Partly as a result of this preference--and, probably, also pollutants that disrupt endocrine and metabolic functions--obesity is epidemic. These victims of our evolutionary history don't have to outrun lions to survive. And modern medicine prolongs the lives of many that in an ancient age would have died young of heart failure or a variety of other problems exacerbated by obesity.

Our evolutionary history affects our perceptions and behavior in many subtle ways. I have neighbors who have surrounded their house with gorgeous horticultural plantings including rare and expensive tropical
varieties. Not a blade of grass grows on their property so the annoying sound of mowing machines never emanates from their surrounds. Yet some other neighbors have let slip occasional snide remarks. Why is that? Psychologist Charles Snowdon told me of an unpublished study in which subjects rated television commercials that included outdoor scenes. The favorites were those where the scene resembled a typical suburban yard of trees providing less than a full canopy and with lawn beneath. The natural habitat most closely matching these characteristics is savannah, such as on the plains of Africa where Homo sapiens originated. We seem to try unconsciously to replicate our ancestral environment in suburbia, and as a result alternative yards (no matter how tasteful) may seem strangely inappropriate to us as places of habitation.

A recent study that was summarized in a health magazine found a new benefit of time in the out of doors, adding to the many we have all heard. Autistic children improved in many ways, including their
communicative behavior, as a function of spending time outdoors. One factor in the mechanism may be higher production of vitamin D, which is created by radiation of sterols, although there may be a whole complex of factors. In my generation, mothers urged their kids to "go out and play," which wasn't entirely an attempt to get them out from under foot. The motivation included an unconscious awareness that growing children need to be outdoors, thus paralleling many home health remedies that have proven their worth when investigated experimentally. Ancestral children grew up in the out of doors; it is the environment to which
their development is adapted.

The Executive Director of the Rocky Mountain Nature Association, Curt Buchholtz, relates the following anecdote in a recent newsletter. He was showing friends (a couple with two sons) around Rocky Mountain
National Park. The boys had their faces buried in battery-powered electronic game machines and could be persuaded to look up only once during the whole tour--to note briefly a herd of elk near the car. The child and family psychiatrist Douglas Kramer recently published an essay reminding us that an individual emerges from childhood as a result of complex interactions of genetic and environmental factors. He points out that if the environment is abnormal--i.e., not the one the genes were adapted to interact withâthen the product will also be abnormal.

In sum, many things about human behavior make little sense except in light of the species' evolution. Failure to take seriously the fact that we are products of natural selection can have adverse consequences. Among other things, we must strive, in my opinion, to "leave no child indoors." People will want to save the planet and its biologically diverse riches if they grow up having frequent contact with the natural world. It is, after all, our real home.